A pulse-based ultra-wideband wireless communication technology is characterized by low power consumption and inherent location awareness. The pulse-based ultra-wideband wireless communication technology was adopted as a physical layer technology of IEEE 802.15.4a, the international standard for low-speed location-aware Wireless Personal Area Network (WPAN), and is considered as a promising technology.
FIG. 1 is a block diagram of a conventional pulse-based ultra-wideband system. Referring to FIG. 1, the pulse-based ultra-wideband system includes a transmitter and a receiver. The transmitter includes an encoder 1, a modulator 2, and an ultra-wideband pulse generator 3, and the receiver includes an ultra-wideband front end/correlator 4, a synchronizer/demodulator 5, and a decoder 6. In addition, the ultra-wideband system includes a switch or duplexer 7 and a clock/timing generator 8.
FIG. 2 illustrates a frequency-domain waveform of an ultra-wideband pulse of 5 GHz or less, which is proposed in IEEE 802.15.4a, and FIG. 3 illustrates a time-domain waveform of an ultra-wideband pulse satisfying the frequency band of FIG. 2.
In order to satisfy the frequency band of FIG. 2, the time-domain waveform of the ultra-wideband pulse generated from the ultra-wideband pulse generator 3 of FIG. 1 has a connection of a plurality of sine waves with a random envelope as shown in FIG. 3. The ultra-wideband pulse generator 3 of the pulse-based ultra-wideband system generally generates a pulse shown in FIG. 4.
FIG. 4 is a block diagram of a conventional ultra-wideband pulse generator using a carrier. Referring to FIG. 4, the conventional ultra-wideband pulse generator shifts the frequency band of the pulse using a Gaussian monocycle pulse 10 and a carrier 11 in order to meet the specification.
Although the conventional ultra-wideband pulse generator can generate the ultra-wideband pulse of FIG. 3, it is inefficient because of the use of a phase locked loop (PLL) that consumes a large amount of power in generating the carrier and occupies a large area. For these reasons, the conventional ultra-wideband pulse generator has difficulty in implementing a low-speed location-aware WPAN with a low cost and low power.
Although the conventional ultra-wideband pulse generator can generate the ultra-wideband pulse of FIG. 3 using an analog device, characteristics of the analog device may be changed or a chip clock and a carrier frequency are not generated by a common source. Therefore, the receiver has difficulty in synchronization reception.